\begin{table}[htbp]\centering
\def\sym#1{\ifmmode^{#1}\else\(^{#1}\)\fi}
\caption{Electoral System, Candidate Communication, and Change in Partisan Affect (Traits)\label{tab:aptpretreat}}
\begin{tabular}{l*{3}{c}}
\hline\hline
                &\multicolumn{1}{c}{(1)}   &\multicolumn{1}{c}{(2)}   &\multicolumn{1}{c}{(3)}   \\
                &Affective Polarization   & In-Group   &Out-Group   \\
                &     b/se   &     b/se   &     b/se   \\
\hline
RCV Compliment  &    0.006   &    0.007   &   -0.004   \\
                &  (0.015)   &  (0.020)   &  (0.022)   \\
RCV Comp. + Endorse&   -0.010   &   -0.030   &   -0.011   \\
                &  (0.016)   &  (0.020)   &  (0.023)   \\
Political Interest&   -0.006   &   -0.001   &    0.011*  \\
                &  (0.003)   &  (0.004)   &  (0.005)   \\
RCV Compliment x Political Interest&   -0.001   &   -0.001   &    0.001   \\
                &  (0.004)   &  (0.006)   &  (0.007)   \\
RCV Comp. + Endorse x Political Interest&    0.003   &    0.009   &    0.003   \\
                &  (0.005)   &  (0.006)   &  (0.007)   \\
Constant        &    0.004   &    0.000   &   -0.008   \\
                &  (0.011)   &  (0.014)   &  (0.016)   \\
\hline
R$^2$           &     0.00   &     0.00   &     0.01   \\
\textit{N}      &     2250   &     2250   &     2250   \\
\hline\hline
\end{tabular}
\end{table}
